Climate science reaches unhappy milestone

One of the world’s most important sentinel sites for measuring levels of carbon dioxide in the atmosphere, in Mauna Loa, Hawaii, reported that levels had risen above the symbolically important figure of 400 parts per million. Because rising amounts of carbon dioxide in the atmosphere have been linked to climate change, scientists suggest that rising above that level makes it harder to prevent global temperatures from rising in accord with the Paris accord. It has been millions of years since atmospheric levels of carbon dioxide have risen so high. Vice Motherboard screamed, “Goodbye World: We’ve Passed the Carbon Tipping Point for Good.” But Ralph Keeling, director of the Scripps CO2 program, stressed that 400 ppm is “a good yardstick,” but “to call it a tipping point is incorrect.”